Bifacial modules - Tracking, horizontal axis E-W

[Virgil Ciolponea]

Dear Team,

I am trying to create a simulation in  PVsyst with Tracking horizontal axis E-W and I have 2 problems:

1) I can not use bifacial modules when I use this configuration for my system. This is the error:  .If I don t use bifacial modules  I can run the simulation without any errors, but I need to do a bifacial simulation.

2) I don't know exactly which one of these variants is correct:

• If I use Tracking horizontal axis N-S and rotate the modules in the shading scene with an -90 azimuth practically resulting an Tracking horizontal axis E-W system.
• On the other hand, the production is slightly higher if I use directly Tracking horizontal axis E-W in the orientation and the shading scene.

Which one of these simulation is correct?

Kindly help me with this situation. 

[Michele Oliosi]

Dear Virgil Ciolponea,

Are you sure you want to use E-W trackers? This type of tracker is more uncommon. NS-axis trackers (turn towards east in the morning and face west in the evening) are more common.

Unfortunately, the bifacial calculation only handles NS-axis SAT at the moment. Even though PVsyst will formally allow turning the N-S axis tracker 90° around, it will not lead to good results, especially in backtracking mode (the backtracking of EW and NS axis trackers are different).

If you need a bifacial gain value, I would suggest extrapolating the values using a fixed tilt variant to establish an approximation of the bifacial irradiance gains.